Using data flow diagrams


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Using data flow diagrams

  1. 1. DATA Flow Approach Conceptualize: “ how data move through the organization “ “ the process or transformation that the data undergo “ “ and what are the outputs “ Data Flow Diagrams (DFDs) ⱷemphasize the processing of data or the transforming of data as they move through a variety of processes.
  2. 2. Advantages of the Data Flow Approach Have 4 advantages 1. Freedom from committing “technical implementation of the system” 2. Further understanding of the interrelatedness of systems and subsystems. 3. Communicating current system knowledge to users 4. Analysis of a proposed system to determine if the necessary data and processes have been defined
  3. 3. Conventions used in DFDs
  4. 4. Developing data flow Diagrams Developing Data Flow Diagrams Using a Top – Down Approach 1. Make a list of a business activities and use it to determine various External entities Data flows Processes Data stores 2. Create a context diagram that shows external entities and data flow to and from the system. Do not show any detailed processes or data stores 3. Draw diagram 0, the next level. Show processes, but keep them general. Show data stores at this level. 4. Create a child diagram for each of the processes in Diagram 0. 5. Check for errors and make sure that labels you assign to each processes and data flows are meaningful. 6. Develop a physical data flow diagram from the logical data flow diagram. Distinguish between manual and automated processes, describe actual files and report by names and add controls to indicate when processes are complete or errors occur. 7. Partition the physical data flow diagram by separating or grouping parts of the diagram in order to facilitate programming and implementation.
  5. 5. 1st Basic rules to follow: 1. Must have at least one process. 2. A process must receive at least one data flow coming into process and leaving from the process. 3. A data store should be connected to at least one process. 4. External entities should not be connected to each other.
  6. 6. 2nd Creating the context diagram 0 System Name Input A Input B Output C D1 Data Store 1 Entity 3 Entity 2 Entity 1
  7. 7. 3rd Drawing Diagram 0 4 General Process DDD 3 General Process CCC 2 General Process BBB 1 General Process AAA D1 Data Store 1 D2 Data Store 2 Entity 1 Entity 2 Entity 3 Data Flow C Data Flow B Record ERecord A Record A Record E Data Flow DInput B Input A Output C
  8. 8. 4th Creating Child Diagrams 4 General Process DDD 3 General Process CCC D1 Data Store 1 Entity 2 Record A Data Flow DInput B 3.2 Detailed Process YYY D1 Data Store 1 Record A Transaction Record 1 3.2 Detailed Process ZZZ Detailed Data Flow Z Data Flow D D5 transaction File 1 3.1 Detailed Process YYY Transaction Record 1 Error Input B
  9. 9. 5th Checking the Diagrams For Error